This project provides statistical support for the design, conduct and analyses of clinical trials in the therapy of malignant diseases conducted by the Acute Leukemia Group B. It also provides operational support to coordinate this cooperative research among 225 clinical investigators working in 42 international centers. These research activities include the statistical functions of experimental design, central randomization, data collection, processing, analysis and presentation, as well as the operational services of typing, printing and distributing study protocols, data collection forms, agenda and minutes of Group deliberations, and the review and exchange of clinical records between investigators. In addition to the initiation of approximately 12 new studies each year and the maintenance of an average 30 active studies, extra-protocol statistical analyses of accrued patient records are conducted. These analyses attempt to identify subsets of patient populations with diverse cancers which exhibit different prognoses under common therapy. Their ultimate goal is to develop mathematical models of these diseases which, in turn, will suggest potentially more effective treatment programs.